You can't use what the Russians did during the Soviet as a good comparison to the UFP. Especially, when both designs are considered failures by Western analysts and both designs were outdated by the time they were actually put into production.

Where would the difference lie? For all we know, Klingon analysts considered both Constellation and Excelsior miserable failures.

A better comparison would be the Freedom LCS vs Independence LCS.

...Ships that are invalid from the very concept on, and both demonstrably miserable failures engineering-wise?

Neither really provides any sort of insurance against the other, either. If one flops, the other will go down in flames as well, being identical to her competition in all the aspects subject to the risk of failure. It's really a case of finding an alternative to the LCS concept, there lamentably being none (at least none that would involve ships).